do you have nero there is a thing called wave editor you can adjust the sound of the cd then reburn it to cd it does all different things its quite good if you dont have it you can download the try ne version fro nero.com

If you create an audio disk using Nero there is a box marked normalise recordings, just tick it, this will do exactly what you want, I think its on the page where you burn,if you look for it you'll find it easily enough

Seems to do what I want - but free version will only do 20 files before wanting payment [I have over 100!]. Will tick this as resolved and consider how to check if the few files it has supposedly 'normalised' have actually been don.